HR: 14:10h
AN: B13G-03    [Abstracts]
TI: A geochemical approach to assessing the relative contributions of rivers, wetlands and island drains to dissolved organic matter in the Sacramento-San Joaquin River Delta
AU: * Kraus, T E
EM: tkraus@usgs.gov
AF: US Geological Survey, California Water Science Center, 6000 J Street, Sacramento, CA 95819, United States
AU: Bergamaschi, B A
EM: bbergama@usgs.gov
AF: US Geological Survey, California Water Science Center, 6000 J Street, Sacramento, CA 95819, United States
AU: Stepanauskas, R
EM: rstepanauskas@bigelow.org
AF: Bigelow Laboratory for Ocean Sciences, P.O. Box 475, West Boothbay Harbor, ME 04575, United States
AU: Hernes, P
EM: pjhernes@ucdavis.edu
AF: Land, Air and Water Resources, University of California, Davis, 1 shields Ave., Davis, CA 95616, United States
AU: Kendall, C
EM: ckendall@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, United States
AU: Spencer, R G
EM: rgspencer@ucdavis.edu
AF: Land, Air and Water Resources, University of California, Davis, 1 shields Ave., Davis, CA 95616, United States
AU: Losee, R F
EM: rlosee@mwdh2o.com
AF: Metropolitan Water District of Southern California, 700 Moreno Avenue, La Verne, CA 91750, United States
AU: Fujii, R
EM: rfujii@usgs.gov
AF: US Geological Survey, California Water Science Center, 6000 J Street, Sacramento, CA 95819, United States
AB: The Sacramento-San Joaquin River Delta (Delta) is a hydrologically complex system which, in addition to being used for crop production, development, and recreation, provides drinking water to over 23 million Californians. Understanding how existing Delta habitats currently affect dissolved organic matter (DOM) dynamics seasonally will help us predict how future changes in land use might influence water quality. This study assessed whether different sources (rivers, wetlands, open water, island drains) contribute DOM to the Delta, examined the composition of the added DOM, and then assessed the relative importance of DOM derived from these sources to the quality of water arriving at Clifton Court for export into the California State Water Project. We used a geochemical fingerprinting approach to characterize the DOM originating from different Delta habitats that employed a number of analyses including absorbance, fluorescence, lignin content and composition, δ13C and δ15N isotopic composition, structural groupings determined by ¹³C-NMR, and specific disinfection byproduct (DBP) formation potential. These qualitative parameters adequately distinguished DOM derived from four distinct sources and, thus, enabled us to use a linear mixing model to estimate the contribution of these sources to DOM exiting the Delta. Comparison of water entering the Delta via the Sacramento and San Joaquin Rivers versus water exiting the Delta at Clifton Court indicated that the Delta was a source of DOM throughout the year, particularly in February, March, and May when concentrations already were high in incoming river water. Water passage through shallow wetlands and subsided islands significantly increased DOM concentrations, while deep open water habitats supporting submerged aquatic vegetation had little discernable effect on DOM concentrations and composition. Wetlands contributed greatest amounts of DOM in the spring and summer, in contrast to the island drains, which appeared to be important sources of DOM during the winter. Results indicate that significant changes in land use, particularly the introduction of shallow wetlands, could alter existing patterns of DOM concentrations in the Delta.
DE: 0428 Carbon cycling (4806)
DE: 0442 Estuarine and nearshore processes (4235)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0493 Urban systems
DE: 0497 Wetlands (1890)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting